Method for preparing light absorption layer of copper-indium-gallium-sulfur-selenium thin film solar cells

1. A method for preparing a light absorption layer of copper-indium-gallium-sulfur-selenium (CIGSS) thin film solar cell, through a non-vacuum liquid phase process, the method comprising the steps of: (1) forming stable clear source solutions of Cu, In, Ga, S, and Se, including (a) forming stable clear source solutions of Cu by dissolving halides of Cu into a solvent selected from the group consisting of at least one of liquid ammonia, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, dimethylsulfoxide, tetrahydrothiophene-1,1-dioxide, pyrrolidone, and a mixture thereof, and adding a solution conditioner therein, wherein said solution conditioner is selected from the group consisting of at least one of chalcogenide of alkali metal and chalcogenide of alkali earth metal; (b) forming stable clear source solutions of In and Ga by dissolving halides of In and Ga into a solvent selected from the group consisting of at least one of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol, 2-methyl-1-butanol, isopentanol, sec-pentanol, tert-pentanol, 3-methyl-2-butanol, and a mixture thereof; and (c) forming stable clear source solutions of S and Se by dissolving ingredients of sulfur and selenium into a solvent selected from the group consisting of at least one of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and a mixture thereof, wherein said ingredients of sulfur and selenium are selected from the group consisting of at least one of elemental S and Se, amine salts or hydrazine salts of S and Se; (2) producing a mixed clear solution of Cu, In, Ga, S, and Se by mixing said stable clear source solutions obtained from (1) according to the stoichiometry ratios of Cu, In, and Ga in formula Cu 1-x In 1-y Ga y Se 2-z S z of the light absorption layer of said CIGSS thin film solar cell, and excess sulfur and/or selenium, wherein 0≦x≦0.3, 0≦y≦1, 0≦z≦2, and the excess degree of S or Se is 0%-800%; (3) using said mixed clear solution of (2) to form a precursor thin film on a substrate through a non-vacuum liquid phase process; and (4) drying and annealing said precursor thin film of (3) to produce a CIGSS compound thin film.

2. The method of claim 1 , wherein said halide of Cu of (1) is represented by the formula MX, wherein M is Cu, and X is one or more halogens selected from Cl, Br and I; or said halide of Cu of (1) is represented by the formula MX 2 , wherein M is Cu, and X is one or more halogens selected from Cl, Br and I; or said halide of In, Ga of (1) is represented by the formula M′X 3 , wherein M′ is In and/or Ga, and X is one or more halogens selected from Cl, Br and I; or said halide of Cu, In, Ga of (1) is represented by the formula MM′X 4 , wherein M is Cu, M′ is In and/or Ga, and X is one or more halogens selected from Cl, Br and I.

3. The method of claim 1 , wherein a) said amine salts of S and Se of (1) are the salts formed by H 2 S and H 2 Se with N—R 1 R 2 R 3 , wherein R 1 , R 2 and R 3 is independently selected from aryl, hydrogen, methyl, ethyl or C 3 -C 6 alkyl; or b) said hydrazine salts of S and Se of step (1) are the salts formed by H 2 S and H 2 Se with R 4 R 5 N—NR 6 R 7 , wherein R 4 , R 5 , R 6 and R 7 is independently selected from aryl, hydrogen, methyl, ethyl or C 3 -C 6 alkyl.

4. The method of claim 1 , wherein said chalcogenide of alkali metal is A 2 Q, wherein A is selected from the group consisting of Li, Na, K, Rb, Cs and a combination thereof, and Q is selected from the group consisting of S, Se, Te and a combination thereof; and said chalcogenide of alkali earth metal is BQ, wherein B is selected from the group consisting of Mg, Ca, Sr, Ba and a combination thereof, and Q is selected from the group consisting of S, Se, Te and a combination thereof.

5. The method of claim 1 , wherein said excess degree of S or Se is 100%-400%.

6. The method of claim 1 , wherein, a mole ratio of a total amount of S and Se to a total amount of Cu, In and Ga ranges from 1.75 to 5 in said mixed clear solution of Cu, In, Ga, S and Se of step (2), and a mole ratio of a total amount of S to a total amount of S and Se ranges from 0 to 0.4 in said mixed clear solution of Cu, In, Ga, S and Se of step (2).

7. The method of claim 1 , wherein said light absorption layer of CIGSS thin film solar cell of (2) has a formula Cu 1-x In 1-y Ga y Se 2-z S z , wherein 0≦x≦0.3, 0.2≦y≦0.4, 0≦z≦0.2.

8. The method of claim 1 , wherein said non-vacuum liquid phase process, which is used in step (3) for preparing said precursor thin film, is selected from the group consisting of spin-coating, tape-casting, spray-deposition, dip-coating, screen-printing, ink-jet printing, drop-casting, roller-coating, slot die coating, Meiyerbar coating, capillary coating, Comma-coating or gravure-coating; or said substrate of (3) is selected from any of the group consisting of polyimide, Si wafer, amorphous hydrogenated silicon wafer, silicon carbide, silica, quartz, sapphire, glass, metal, diamond-like carbon, hydrogenated diamond-like carbon, gallium nitride, gallium arsenide, germanium, Si—Ge alloys, ITO, boron carbide, silicon nitride, alumina, ceria, tin oxide, zinc titanate and plastic.

9. The method of claim 8 , wherein said precursor thin film is annealed at a temperature of 250-650° C.

10. The method of claim 1 , wherein said precursor thin film is annealed at a temperature of 50-850° C.

11. The method of claim 10 , wherein said precursor thin film is annealed in Se atmosphere at a temperature of 450-600° C. for 10 to 60 minutes, and in S atmosphere at a temperature of 350-550° C. for 10 to 60 minutes.

12. The method of claim 1 , wherein a thickness of said CIGSS compound thin film of step (4) is 5-5000 nm.

13. The method of claim 1 , wherein said adding said solution conditioner thereby stabilizes said clear stable source solutions.